1. Field of the Invention
The present invention relates to a fuel cell system and a method for permitting an idle stop in the fuel cell system, and more specifically, to a fuel cell system where an idle stop is performed and a method for permitting the idle stop in the fuel cell system.
2. Description of the Related Art
In recent years, a solid polymer type fuel cell has been a focus of attention as a power source of an electric vehicle, and so on. The solid polymer type fuel cell is a stack of cells each of which is formed of a solid polymer electrolyte membrane sandwiched between a pair of electrodes (an anode and a cathode). In a fuel cell system including such a fuel cell, hydrogen (fuel gas) supplied to the anode is ionized on a catalyst layer and emits electrons. The electrons are taken out of an outside circuit where the electrons are flowing toward the cathode, to be used as direct current electric energy. Hydrogen ions migrate to the cathode through the solid polymer type electrolyte membrane. Then, the hydrogen ions are combined with air (oxidizing gas) supplied to the cathode and the electrons which have come through the external circuit, so as to generate water.
A vehicle equipped with such a fuel cell system has a technology for permitting an idle stop depending on states of driving speed, output power, and brake operation in order to improve fuel cost (See JP2001-359204 A, for instance). In the technology, when it is detected that the vehicle is being idle, supply of air to the fuel cells is stopped so that the power generation of the fuel cells is stopped.